The present invention relates to a valve and, more particularly, to a valve for controlling opening or closing of a fluid passage in pipes.
A valve is generally used in pipes to control opening or closing of a fluid passage in the pipes conveying a fluid. When the components of the valve malfunction due to corrosion by the fluid in the pipes or due to aging, maintenance of the valve is required to avoid loss resulting from leakage of the fluid.
FIG. 1 shows a conventional valve 10 including a body 12, a cap 14, and a top seat 16 mounted on top of the cap 14. The body 12 includes an inlet 17 and an outlet 18 for connection with pipes conveying a fluid. A chamber 19 is formed in a top portion of body 12. A valve rod 20 includes a lower end 22 extending into the chamber 19 and connected to a plug 24. A hand wheel 28 is mounted to an upper end 26 of the valve rod 20. A sleeve 29 is provided in a center of the hand wheel 28 and receives the upper end 26 of the valve rod 20. The sleeve 29 is fixed by a fastener 30 to the top seat 16. When a user rotates the hand wheel 28, the valve rod 20 and the plug 24 move upward or downward to open or close the fluid passage between the inlet 17 and the outlet 18. The cap 14 is fixed by screws 31 to the top portion of the body 12. A pressing block 32 is mounted on top of the cap 14. Fillers 34 are mounted in the cap 14 and sandwiched by bushings 36 on upper and lower sides of the fillers 34. When two nuts engaged on two tightening bolts 38 are rotated to press against the fillers 34 via the pressing block 32 and the upper bushing 36, the fillers 34 seal a gap between the valve rod 20 and the cap 14, avoiding leakage of the fluid via the chamber 19.
However, the body 12 and the cap 14 are formed by casting and, thus, have voids in inner faces thereof. The voids turn into slits due to chemical corrosion after a period of time, resulting in leakage of the fluid. Furthermore, the fastener 30 and the top seat 16 include threads 39 that are liable to get stuck due to rusting resulting from dust, particles, and moisture in the air, such that the hand wheel 28 can not be rotated. For a valve in a factory near a sea, the threading engagement section between the fastener 30 and the top seat 16 and the threading engagement section between the valve rod 20 and the sleeve 29 are liable to get stuck due to corrosion by the sea wind. Thus, the hand wheel 28 can not be rotated to move the valve rod 20 and the plug 24. Further, to allow smooth upward/downward movement of the valve rod 20, the valve rod 20 is in loose coupling with the fillers 34 and the bushings 36. To allow replacement of the fillers 34 without stopping the machine, the fillers 34 are generally C-shaped in cross section and have an opening. After removing the damaged fillers 34 out of the cap 14, new fillers 34 can be mounted around the valve rod 20 into the cap 14 via the opening of each filler 34 without the need of mounting through the upper end 26 of the valve rod 20. However, the openings of the fillers 34 adversely affect the sealing function of the fillers 34 and make themselves vulnerable.